International Produce Training

Lemons-Internal Decline

Every now and then you come across a defect that you have no idea what it is, or what caused it.  Internal decline in lemons is one of these defects.

This defect occurs in June or July and is evident until September or October, although it has been reported as early as March and as late as November.  Pathologists will refer to this defect as Endoxerosis.  It is a is a common phenomenon in California lemon groves in summer, particularly in the hot inland valleys.  The first sign of endoxerosis in the lemon is formation of cavities adjacent to the vascular bundles in the stylar region (opposite of the stem end) of the peel (Bartholomew, Barrett, and Fawcett, 1923). After formation of the cavities, a colorless, gummy substance is exuded which may clog some of the xylem vessels (Bartholomew, 1928a).

So, what does the USDA say about Internal Decline?

This condition usually occurs at the stylar-end and is frequently accompanied or followed by Alternaria rot. Symptoms of this disease include a breaking down or drying of internal tissue of the stylar end and can be accompanied by a pinkish to brownish gummy mass. Gum formation in the core and in or next to the peel is also common. Any amount is scorable in all grades.

To break this down, the USDA does not say all Internal Decline is decay, but Internal Decline may lead to decay.  If you encounter this defect you will have to cut the lemons is half, either cross-wise or length-wise to examine the fruit.  You may find the core being slightly discolored, and because the USDA says this a “free from defect” you should score the lemon as a defect, Internal Decline.  You are allowed 12% of the lemons with defects, including Internal Decline.  If you find the discoloration is breaking down, the tissue disintegrates when rubbed between your fingers, you should score the lemon as decay.  The U.S. Standards of U.S. No. 1 allow no more than 3% decay.

Bottom line, don’t forget to cut some lemons while inspecting, looking for Internal Decline.  And if you do find Internal Decline be careful to check to see if the disorder is breaking down into decay.


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